Plutonium is a man-made radioactive element which is used as an explosive ingredient in nuclear weapons and as a fuel for nuclear reactors. It has the important nuclear property of being readily fissionable with neutrons and is available in relatively large quantities. Caution must be exercised in handling plutonium to avoid unintentional formation of critical mass. Plutonium in liquid solutions is more apt to become critical than solid plutonium, so it is also very important to avoid the unintentional creation of a liquid solution. Since plutonium is considered to be highly carcinogenic, it is important that plutonium in any form be contained and not escape into the surrounding environment where it can be inhaled or otherwise ingested by humans or other living things. Frequently, plutonium oxides and salts are in the form of powders which require very special handling to ensure that particles do not become suspended in the air and that liquid does not come into contact with the powders. It is also very important that, if fluid occurs in or develops in the powders, that containers holding the powders are vented.